The present invention relates to a device for controlling the speed of a motor vehicle in which a power setting member for the internal combustion engine of the vehicle can be adjusted by an electric motor via a switchable coupling. The electric motor receives the voltage necessary for displacing the power-setting member for the speed which is to be maintained from a control device, and the coupling is adapted to be switched by means of an electromagnet in such a manner that the motor is separated from the power-setting member when the device for controlling the speed is not active.
In devices for controlling speed--in the following also referred to as speed control systems--it is important, in addition to obtaining reliable manner of operation as such, that the driver be informed that the speed control system was in action, i.e. that when the speed control system is in action, he should not be driving with the belief that the speed control system is not active.